1. Field of the Invention
This invention relates to plastic encapsulated integrated circuit die packages. More particularly, this invention relates to formation of a multilayer ground plane assembly for an integrated circuit package which is capable of also providing heat dissipation and mechanical support for the package as it is being formed.
2. Description of the Related Art
In the packaging of integrated circuit structures, it is known to provide metal portions adjacent the integrated circuit die which electrically function as ground planes to reduce inductance, and thereby speed the performance of the device, as well as to provide a heat sink or dissipation means.
For example, Andrews U.S. Pat. No. 4,147,889 discloses a chip carrier comprising a printed circuit board having a metal layer formed on each surface. The metal layer on one surface comprises an external heat sink of substantial surface area while the metal layer on the side to which the chip is bonded is patterned to form lead fingers and a central metal heat sink to which the chip is bonded. According to the patentees, holes may be provided through the printed circuit board which are subsequently filled with metal to provide a direct metal contact between the heat sink to which the chip is bonded and the external heat sink.
Butt U.S. Pat. No. 4,410,927 teaches a casing for an electrical component such as an integrated circuit die with a metal base member onto which the die is bonded using an epoxy adhesive. A lead frame is also sealed and bonded to the metal base member. A metal housing member is mounted upon the base member to form an enclosed casing.
Daniels et al U.S. Pat. No. 4,680,613 discloses a low impedance package for an integrated circuit die comprising a lead frame without a central paddle and a ground plate which forms the die attach plane and which is spaced from and parallel to the lead frame. A dielectric layer is formed between the lead frame and the ground plate.
Katagiri Japanese Patent document 59-207645 discloses a semiconductor device and lead frame wherein a heat dissipating plate is connected to a semiconductor chip through a mounting agent which is a good heat conductor. After connecting the chip to leads via wires, the chip and leads are sealed by a resin mold layer so that the surface of the heat dissipating plate is exposed.
Usually, however, it is more difficult to incorporate a metal ground plane/heat sink into a plastic-encapsulated integrated circuit package because of the difficulty of orienting and mechanically assembling together the integrated circuit die, lead frame, and ground plane/heat sink prior to the encapsulation step which will then serve to provide the mechanical bonding together of the components comprising the package.
It would, therefore be desirable to provide a plastic-encapsulated integrated circuit package incorporating therein an electrical ground plane/thermal heat sink and a method of assembling such a structure which will provide a mechanically stable and strong structure prior to encapsulation.